Method and apparatus for scoring cover glass



Dec. 19, 1944. G w s, 2,365,503

NOW BY JUDICIAL CHANGE OF NAME T. G. WHITE METHOD AND APPARATUS FOR SCORING COVER GLASS Filed March 27, 1942 5 Sheets-Sheet l I I5! 55 L .HIIHH HE I I I. H IE A 22 5] a 29 52m ILII IE! I III I IE! I l 41 1 I l 68 I I l I I I 49 I I F l Y. E11: 58

Dec. 19, 1944. -1s, 5,

NOW BY- JUDICIAL CHANGE OF NAME T. G. WHITE METHOD AND APPARATUS FOR SCORING COVER GLASS Filed March 27, 1942 3 Sheets-Sheet 3 QQN R, mm

m wN W Patented Dec. 19, 1944 METHOD AND APPARATUS FOR SCORING COVER GLASS Theodor G. Weihs, Pittsburgh, Pa. now by judicial change of name Theodore G. White, assi'gnor to American Window Glass Company, Pittsburgh, Pa., a corporation of Pennsylvania Application March 27, 1942, Serial No. 436,425

Claims.

This invention relates to the production of cover glass, i. e., thin sheet glass, .005" to .007 thick, insmall pieces cut accurately to size and usually square or rectangular in shape.

Cover glass is produced in roughly circular sheets 8 or larger in diameter and must be cut to size. before it is ready for shipment to-the user. Heretofore, so far as I am aware, hand scoring and breaking of the sheet has been the only method of cutting cover glass to size. The flexibility and fragility of the material resulting from its small thickness introduce considerable difiiculty into the cutting operation and it is for this reason that, although machines have been designed for cutting window glass and the like to size, it has proved impossible to utilize such machines for cutting cover glass.

The cutting of cover glass by hand is open to serious objections. In the first place, it requires a high degree of skill and the laborcost of the operation is high because only a relatively limited output is obtained per man-hour. In the second place, the cutting by hand introduces slight variations in the size of the pieces as a result of the fact that the cutting tool as it traverses the scoring guid is not always held. at a constant angle to the sheet being scored. In addition, the pressure applied to the scoring tool by the cutter often varies in different ortions of the stroke of the tool. If th pressure is below a certain value, there is less likelihood that a clean break will result. If the pressure on the tool is excessive, the sheet may shatter causing a loss of material. There are several reasons why it has proved impossible to score cover glass by machines which have been developed .for scoring thicker grades of sheet glass. One of these is the fact that cover glass sheets as delivered for scoring are highly irregular in outline. In. addition, the fragility of the material presents a serious problem in the matter of mere handling and holding in position during scoring, without excessive breakage. tools are advanced into engagement with the edge of a sheet disposed at right angles to the path of the tools and the latter ride up over the edge and commence scoring immediately. Thi mode of operation cannot be adopted in scoring cover glass because of the aforementioned irregularity in the shape thereof. By reason of this irregularity, a cutting tool advancing toward a. sheet of cover glass might engage an edgemaking a very acute angle with the path of the tool whereby excessive lateral pressure would be exerted by the tool and the sheet possibly shattered, since the In most cutting machines, scoring tool would tend to dig? into the sheet instead of riding up over the edge and immediately commencing a score.

broken by hand into accurately sized pieces of the desired dimensions and shape, at a production rate per man-hour considerably higher than the best results obtained by hand scorin and with a higher percentage yield of salable material. In a preferred practice of the invention, I dispose a sheet of cover glass, on a carrier plate or support having perforations therethrough and induce a flow of air through said perforations to hold the sheet on the support frictionally. I then lower a scoring tool into engagement with the surface of the cover glass sheet at a point spaced inwardly from the edge thereof and traverse it across the sheet, guiding it accurately along a predetermined path and maintaining a uniform pressure thereon. I repeat this operation to form a plurality of spaced parallel scores in groups intersecting each other at right angles and then remove the support and sheet from the scoring position. The scored sheet is then passed to a severing or breaking position at which it is broken along the scores, into a plurality of accurately sized pieces of the required shape and dimensions.

My invention has utility chiefly in connection with the apparatus disclosed herein which is also disclosed and some features thereof claimed in the co-pending application of Norman E. Klages, Serial No. 434,730, filed March 14, 1942, for Apparatus for scoring cover glass, on which Patent 2,357,206 issued August 29, 1944.

A complete understanding of th invention, its

details, novel features and advantages, may be had by a consideration. of the following descrip tion and explanation referring to the accompanying drawings illustrating apparatus adapted for the carrying out of. the invention.

In the drawings,

Figure 1 is a plan view of a scoring apparatus embodying the principles of my invention;

Figure 2 is a side elevation;

Figure 3 is a view partly in end elevation and partly in section along the plane of line III-III of Figure l;

form of apparatus for carrying out the method of my invention comprises a base or frame III having a top or working surface I I and supporting legs I2. The base It may conveniently be a casting and has side flanges or webs I3 extending between the legs I2.

A well or depression I4 is formed in the top II of the base and is adapted to receive a circular turn-table I5. body It having a perforated cover plate I'I secured thereon. A central stud I8 extends downwardly from the table and into a hub I9 formed on the bottom of th well I4. The cooperating surfaces of the stud and hub are correspondingly tapered to provide a fairlyclose fit. A pipe 25 is threadedinto the hub I9 and provides a con- The table I includes a hollow air is drawn through the perforations remaining uncovered by the glass sheet with some leakage of air between the sheet and the carrier plate into the perforations cove-red by the former. As shown in Figur 1, the sheet covers a greater or lesser area of the plate 28, depending on its size and outline. Since I employ a relatively low degree of vacuum or suction and a suction device having a relatively large capacity, the air drawn through the uncovered perforations may readily be exhausted from the hollow interior of the table I5. The resulting vacuum below the glass sheet leaves the pressure of the air thereabove unbalanced whereby the sheet is pressed against the carrier plate with sufficient force to grip it frictionally and resist sliding under the horizontal nection to a suitable source of suction as will be I explained more fully hereafter. Roller brackets 2I are secured below the top II adjacent the well I I and in circumferentially spaced relation therearound. The side wall of the well It is recessed as at I ia to admit the lower, inwardly projecting portions of the brackets. Bearing rollers 22 are journaled 0n screw shafts 23 threaded into horizontal tapped holes in the brackets 2| and support the table I5 for rotation. The bottom of the table is machined as at E l to provide a raceway engaging the rollers 22. Centering rollers 25 are journaled on screw posts 25 inserted through holes in the top II and threaded into vertical tapped holes in the brackets 2i. The rollers 25 engage the periphery of the table I5 and keep it properly centered in the well I l as it turns on the bearing or supporting rollers 22. The portions of the shafts 23 and posts 26 on which the rollers 22 and 25 are disposed may be eccentric with respect to the axes of the shafts and posts whereby the rollers 22 may be adjusted vertically and the rollers 25 horizontall on rotation of the shafts and posts, respectively.

The perforations in the cover plate I? are indicated at 2'! and are preferably distributed over the surface thereof uniformly. A carrier plate 28 is removably disposed on the cover plate II and has perforations 29 formed therein adapted to register with theperforations 2! when the plate is disposed on the table concentrically thereof.

.To facilitate proper placement of the plate on the table, the latter has pins 30 spaced circumferentially thereof adapted to enter suitable holes in the late. By virtue of the construction described, a sheet of cover glass 3I may be disposed on a carrier plate 28 before the latter is disposed on the table I5. On placement of the carrier plate and induction of air through the perforations 2'! and 29 remaining uncovered by the sheet 3!, the latter is held against the carrier plate by air pressure with sufficient force 'to hold it frictionally against sliding under horizontal forces of the order of those produced by traversing a scoring tool across the sheet.

For inducing a flow of air through the perforations 2'! and 29 into the hollow interior of the table I5 and outwardly thereof through the stud I8 and pipe connection 20, I employ an airexhaust or suction pump capable of handling a relatively large volume of air and maintaining only a moderate degree of vacuum. For example, I have successfully employed a household suction cleaner having a capacity of between and cubic feet per minute and capable of maintaining a vacuum of about 45 inches of water. It will be apparent that, when using such a.device,

force exerted thereon by a scoring tool.

Since cover glass is usually marketed in the form of square or rectangular pieces, I provide means for securely locking the table I5 in two scoring positions at right angles to each other. Sockets 3?. are bored radially into the periphery of the table I5 and are spaced apart 90 circumferentially thereof. Index plugs 33 are inserted in the sockets 32 and are provided with tapering recesses in their outer ends. An index plunger 34 having a pointed inner end adapted to enter the recesses in the outer ends of the plugs 33, is slidable axially in a guide sleeve or tube 35 which may conveniently be formed integral with the top II of the base Ill. The index plunger is normally urged inwardly by a compression spring 36 disposed about a reduced stem 37 extending rearwardly from the plunger 34. The spring is held in position by a plug 33 threaded in the outer end of the tube 35. A thumb lever 39 is pivoted to the end of the stem 3I projecting through the plug 38 and also to a bracket 40 secured to one of the webs I3 of the base It).

When the plunger 34 is in the position shown in Figure 5, it locks the table I5 against rotation by virtue of the engagement of the plunger with the plug 33. When it it desired to rotate the table I5, it is only necessary to press outwardly on the upper end of the lever 39 and then turn the table as desired by hand. If the table is to be turned 90, the release of the lever 39 when an adjacent plug 33 is in alinement therewith serves to lock the table in a position at exactly 90 to its former position.

Having explained the turn table or rotatable support for the glass sheet to be scored and the manner of securing the sheet thereto, it now remains to explain the provisions for scoring the sheet.

Rails II and 42 extend along opposite sides of the working surface I I. A traveling bridge indicated generally at 43 is adapted to move along these rails. The bridge comprises brackets 44 and 45 and upper and lower tie rods 46 and 41 extending therebetween. Supporting rollers 49 are journaled on shafts 55 extending inwardly from the brackets 44 and 45 and rest on the upper edges of the rails 4| and 42. Hold-down rollers 5| are similarly mounted and engage the lower -move it is applied manually to only one end thereof, I provide chains 52 having their ends pinned to the lower ends of the brackets 44 and 45 and trained around sprockets 53 adjacent the aseasos 3 ends of the-path of the bridge. The sprockets 53 are keyed to shafts 54. extending across the base Ill below the top II thereof and journaledin bearings 540. secured to the inner surface of the webs l3. It will be apparent that movement of either end of the bridge 43 immediately turns the sprockets and thereby produces an equal and simultaneous movement of the other end of the bridge. A stop screw 55 is threaded through a lug 56 depending from rail 4| and is adapted to engage roller 51 on bracket 44 and thereby serves to limit movement of the bridge 43 toward the lever 39.

A slide 51 is movable along the tie rods 45.

The slide has a knob 58 adapted to be engaged by the palm of the operator's hand, for causing movement of the slide. A lever 59 pivoted to the slide at 69 serves as a tool holder and has a knob BI at the upper end thereof which may conveniently be engaged by the forefinger of the hand of the operator which engages the knob 58 on the slide. A tool mount 62 is secured to the lever 59. A scoring tool 63 is positioned in the mount 62 in such relation thereto as to engage the sheet 3| as the slide moves along the tie rods 46. The lever 59 is normally urged clockwise as viewed in Figure 3 by a tension spring 64 secured thereto and also to an adjusting screw 65 extending through one side of the slide and having a knurled adjusting nut thereon. A stop screw 66 threaded through a lug 61 limits clockwise'movement of the lever 59.

In order to hold the bridge 43 in properly spaced position along the length of the working surface II, I provide a gauge bar 68 secured to and extending along the rail 4|. The bar 68 has transverse notches 69 formed therein at suitable intervals therealong; A gauge lever 19 is pivoted to a clevis 1| secured to bracket 44 and has a projecting portion or finger 12 adapted to enter the slot 69. A spring 13 secured to the lever and the bracket 44 normally urges the lever clockwise as viewed in Figure 3. A screw 14 is threaded into a horizontal hole in the slide 51 adjacent the knob 58. The screw has a lock nut thereon for locking it in adjusted position. When the slide is in the position shown in solid lines in Figure 3, the lever 10 is shifted so that the projecting portion or finger 12 thereof is withdrawn from engagement with the gauge bar 68. When the slide has been advanced slightly, the spring 13 causes the finger 12 to engage the bar 69 and enter the first slot 69 therein with which it is thereafter alined.

The operation of the apparatus, while probably apparent from the description thereof, will now be briefly reviewed. A glass sheet such as that indicated at 3| having been placed on the plate 28 after removal of the latter from the table l5, the plate is replaced on the table so that the holes in the plate aline with those in the cover plate I1 of the table I5. Suction is then applied to the interior of the table by means of a suitable control valve or by starting the suction pump. The glass sheet is thereby frictionally held on the table in position for scoring.

The operator then places his hand on the knob 58 of the slide 51 and with the forefinger of the same hand tilts the lever 59 to raise the tool 63. With the slide in the position shown in solid lines in Figure 3, the bridge 43 is positioned adjacent one side of the sheet 3|. The slide is then moved forward slightly and the bridge traversed back and forth through a small distance until the finger 12 of the lever 10. enters one of the. slots 59 in the gauge bar 68. The slide 51isthen positioned, as shown in chain lines in Figure 3, so that the tool 63 is spaced slightly inwardly of the edge of the sheet remote from the operator. The lever--59 is then releasedgently whereupon the tool 63 engages the sheet. The slide 51 is then moved toward the position shown in solid lines in Figure 3 with the result that the tool 63 produces a straightv score across. the surface of the sheet with a high degree of precision.

It will be apparent thatcompletion of the: traversing movement of the slide 51 automatically causes the lever 19 to disengage the bar 68' as above explained whereupon the bridge is ready for movement to the position for making the next score. The procedure described is then repeated until the entire surface of the glass sheet has been scored along spaced parallel lines; The sheet is then ready for the formation of a second similar set of scores at. right angles. To accomplish this, the lever 39 is tilted to free the table l5 for rotation. After the table has been turned through it 'is again lockedin position by releasing the lever 39. The scoring operation-is then repeated, producing a second set of parallel scores at right angles to thatfirst formed.

It will be noted that the scoring tool exerts a pressure on the glass sheet which is substantially unvarying regardless of. small variationsrin the thickness of the glass sheet itself. This is because the pressure exerted by the tool is-dete'rmined by the torque applied to the lever59 by the spring 64 and that is constant for minor changes in the angular position of the lever such as would result. from high and low spots inxthe surface of the sheet being scored.

When the sheet 3| has been scored in both-directions, the plate 28 with the scored sheet thereon isremoved from the table I5, the bridge 43 having been disposed to one side of the base. The suction applied to the table may first be shut off to facilitate removal of the plate. Immediately the plate 28 has been removed, another similar plate having a glass sheet thereon is placed on the table and scoring thereof is commenced. At the same time, the previously scored sheet is passed along to an operator Whose sole function is to break the sheet along the scores formed therein and stack the perfect pieces for packin and shipping. The removal of the plate 28 from the table l5 equalizes the air pressure on both sides of the sheet 3| and thus permits the latter to be easilyremoved from the plate and severed into small pieces. By the procedure described, the scoring device operates practically full-time without interruptions or loss of time for severance of the scored pieces or cleaning up the scrap. This makes possible a greater output per manhour and reduces the labor cost because the severing or breaking operation requires little or no skill. As a matter of fact, unskilled labor may be trained in the practice of the scoring method and in the use of the apparatus disclosed, in a very short time.

A modification of a detail is illustrated in Figure 6. According to the modification, the joint between the stud I8 of the table I5 and the hub I9 of the well I4 is sealed by a gland 15 disposed in a counterbore in the hub I9 and compressed against the stud I8 by a compression ring 16 secured to the top face of the hub by screws 11. This modification will ordinarily not be necessary although it may be provided if desired to limit the leakage of air between the stud l8 and hub l9.

It will be apparent from the foregoing description and explanation that the invention is characterized by numerous advantages over the prior practice in scoring and severing cover glass. In the first place, the invention makes it possible for two operators, one scoring and one breaking, to produce twice as much cover glass as two operators cutting by hand, each breaking the sheets after scoring thereof. The scoring apparatus disclosed is free from human errors and its precision is limited only by the tolerances permitted in the finishing of machine parts which can be made almost negligible. The percentage of salable material produced by the aid of the invention is greater than that produced by hand cutting methods because the uniformit of the pressure on the scoring tool practically eliminates accidental shattering of a sheet during scoring. The difliculty in the application of machine scoring to cover glass is overcome by making the scores individually and by lowering the scoring tool into contact with the glass sheet at points spaced inwardly from the edge thereof. The ability to operate the machine rapidly may be acquired with a little practice but requires no special skill.

The invention is particularly useful in the scoring of cover glass along straight lines for severance into square or rectangular pieces, It may also be employed, however, for cutting discs of cover glass by appropriately placing th scoring tool and rotating the table with the glass sheet thereon.

Although I have illustrated but a preferred embodiment of the method and apparatus of my invention with a modification of a detail of construction, it will be understood that changes in the construction and operations disclosed may be made Without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In an apparatus for scoring glass sheets, a table for supporting a sheet in position for engagement by a scoring tool traveling across said sheet, said table including a perforated top plate, a suction chamber therebelow and a perforated carrier plate removably disposed on said top plate and adapted to receive a sheet to be scored.

2. In an apparatus for scoring glass sheets, a table for supporting a sheet in position for engagement by a scoring tool traveling across said sheet, said table including a perforated top plate, a suction chamber therebelow, a perforated carrier plate removably disposed on said top plate and adapted to receive a sheet to be scored and means holding said carrier plate so its perforations register with those of said top plate.

3. In a method of scoring thin, flexible sheet glass such as cover glass, the steps including depositing a sheet on a perforated carrier, depositing the carrier and sheet on a perforated support, effecting a suction of air through the support and carrier, scoring the sheet while held in frictional engagement with said carrier by the pressure of the air thereabove, then removing said carrier from said support and removing the scored sheet or severed pieces thereof from said carrier.

4. In a method of scoring thin, flexible sheet glass such as cover glass, the steps including depositing a sheet on a perforated carrier, depositing the carrier and sheet on a perforated support with the perforations of the carrier registering with those of the support, effecting a suction of air' through the support and carrier principally through the holes therein remaining uncovered by the sheet, scoring the sheet while held in frictional engagement with said carrier by the pressure of the air thereabove, then removing said carrier from said support and removing the scored sheet or severed pieces thereof from said carrier.

5. In a method of scoring thin, flexible sheet glass such as cover glass, the steps including depositing a sheet on a perforated carrier, depositing the carrier and sheet on a perforated support, effecting a suction of air through the support and carrier, scoring the sheet while held in frictional engagement with said carrier by the pressure of the air thereabove, then lifting said carrier from said support and lifting the scored sheet or severed pieces thereof from said carrier.

TI-IEODOR G. WEIHS. 

